| The mechanical stirring reactor is widely used and plays a very important role in industries,such as chemical,pharmaceutical,etc.,The stirrer is an important part of the stirred reactor and it has a direct influence on the stirring flow field characteristics and mixing efficiency.Traditional stirrers are mostly made from rigid materials,such as carbon steel,structural steel,etc.This type of rigid blade has problems of large shear force and low energy transfer efficiency when it is used to stir fluid medium.In this project,based on the principle of bionics,the flexible blade Rushton impeller was obtained by using the flexible blade instead of the rigid blade.Using CFD numerical simulation and experimental tests,the power consumption,structural stress,blade deformation and flow field characteristics of the two kinds of impellers were compared and analyzed.The working characteristics of the flexible blade Rushton stirrer was studied.In this paper,the structure of the stirred reactor was determined firstly.The laboratory-scale stirring tank was designed and the structural dimensions of the stirrer were determined according to the proportional relationship of the design manual.The choice of flexible materials is the key to the success of the subsequent research work.Using the elastic modulus of the rigid blade material as the reference value,four different materials were selected.Through the fluid-solid interaction analysis,the results showed that the rubber material paddles have the better adaptivity in the work process and it was determined as the material of flexible blade.The power consumption,blade stress and deformation of the two types of propellers were analyzed by using CFD numerical simulation and experimental testing techniques.The results showed that the power member of the flexible impeller is greater than that of the rigid paddle when the ? 100.During 100<e<10000,the power member of the flexible impeller is less than that of the rigid paddle and the the maximum of the reduction ratio is 17.2%,it also means the power consumption of the flexible impeller is smaller.When the Re?10000,the power number of the two kinds of impellers is basically constant,but the flexible impeller is still smaller.Through CFD fluid-structure coupling technology and particle image velocity tests,The steady flow field characteristics(the velocity field,turbulent kinetic energy,turbulent dissipation rate and trailing vortex)were obtained by operating two kinds of propellers in low-viscosity medium water and high-viscosity medium glycerol.The results showed that the maximum flow velocity of the flexible propeller decreases by 8.94%in the low viscosity stirring medium,but the axial velocity and radial velocity at the vicinity of the stirring tank were increased.In the high viscosity stirring medium,the maximum velocity were increased by 5.4%and the velocity component in the overall tank was larger than that of traditional impeller.In terms of turbulent kinetic energy and turbulent dissipation rate,flexible propellers have lower turbulent kinetic energy and lower dissipation rate in low viscosity fluids,while the turbulent kinetic energy is 26.7%higher than that of rigid impeller in high viscosity fluids.The turbulent dissipation rate of the flexible paddle near the blade is large.As for the trailing vortex,the vortex energy of the flexible paddle is smaller and the vortex structure is more apparent in the low viscosity medium. |
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